Conventionally, many heat pump type refrigeration cycle systems are provided with an expansion valve arranged at an outdoor heat exchanger (i.e. an outdoor unit). In this case, a refrigerant which is expanded by the expansion valve flows into an indoor heat exchanger through a long pipe conduit. Thus, a pressure loss occurs in the expanded refrigerant, causing difficulty in controlling the flow rate at the expansion valve. This is the same for the case when the expansion valve is provided at the indoor heat exchanger.
Meanwhile, Japan Patent Application Publication No. 2009-287913 discloses a heat pump type refrigeration cycle system having expansion valves which function to control, i.e. reduce, the flow rate at the indoor heat exchanger during a cooling mode and reduce the flow rate at the outdoor heat exchanger during a heating mode.
The expansion valve disclosed in the above-mentioned Japan Patent Application Publication No. 2009-287913 is provided with a valve seat member (2, 8) as a sub-valve in order to reduce the flow rate of the refrigerant in a first flow direction of the refrigerant and allow a high flow in a second flow direction while reducing the pressure loss as much as possible. The valve seat member (2, 8) is arranged to slidably move in a direction of an axis in a valve housing (1, 7).
However, for the expansion valves disclosed in the above-mentioned Japan Patent Application Publication No. 2009-287913, there is a problem that since the valve seat member (2) is a thick member and heavy, it has difficulty in operation of moving away from a second port (12). On the other hand, the seat valve member (8) according to another embodiment which is formed by press work is a lightweight member, and thus it operates smoothly when moving away from a second port (72). However, since this valve seat member (8) is provided with a valve port (81a) which is also formed by press work, it is difficult to provide accuracy in a diameter and shape of the valve port (81a), causing an increase in risk of valve leakage between the valve port (81a) and a valve body (51).